In line with the family-friendly Narnia books, or even as far as Lord of the Rings, lease keep the violence to a PG-13 level at most, and no cussing or sex, please.

Writing style is less short and turn-based, like a D&D game, than it is more prose-based, where you can write what other people's characters are thinking and saying. No outrageous changes to someone else's character without their permission, though.